Scanned beam imagers are a promising imaging technology that function by scanning a beam of light over a FOV, collecting the reflected light from the FOV into an optical sensor, and forming a digital image based on the characteristics of the reflected light. Scanned beam imagers may offer a greater range and depth of field, reduced motion blur, enhanced resolution, extended spectral response, reduced cost, reduced size, lower power consumption, and improved shock and vibration tolerance.
FIG. 1 shows a block diagram of a scanned beam imager 10 in accordance with the prior art. The scanned beam imager 10 includes a light source 12 operable to emit a beam of light 14. A scanner 16 is positioned to receive and scan the beam 14 across a FOV 11 as a scanned beam 18 having a fixed beam waist distance. Instantaneous positions of the scanned beam of light 18 are designated as 18a and 18b. The scanned beam 18 sequentially illuminates spots 20 in the FOV at positions 20a and 20b, respectively. While the scanned beam 18 illuminates the spots, a portion of the illuminating scanned beam 18 is reflected (e.g., specular reflected light and diffuse reflected light also referred to as scattered light), absorbed, refracted, or otherwise affected according to the properties of the object or material at the spots to produce reflected light 22a and 22b. A portion of the reflected light 22a and 22b is received by one or more detectors 24, which generates electrical signals corresponding to the amount of light energy received. The electrical signals drive a controller 26 that builds up a digital representation of the FOV and transmits it for further processing, decoding, archiving, printing, display, or other treatment or use via interface 28.
One promising application for a scanned beam imager is in an endoscope.
Endoscopes are typically flexible or rigid devices that have an endoscope tip including a viewing device. The endoscope tip is inserted in a body cavity for viewing anatomical features of the cavity. The viewing device is typically a device, such as a video camera or a scanned beam imager. Electronic or optical signals associated with the images taken by the viewing device are sent up a flexible tube to a console for display and viewing by a medical professional such as a doctor or nurse.
Scanned beam endoscopes that employ scanned beam imager technology are a fairly recent innovation, and an example of a scanned beam endoscope is disclosed in U.S. patent application No. 10/873,540 (“'540 Application”) entitled SCANNING ENDOSCOPE, hereby incorporated by reference and commonly assigned herewith.
The scanned beam endoscope disclosed in the '540 Application scans a beam across a FOV having a fixed beam waist distance from the distal end of its endoscope tip.
While the scanned beam imager 10 and the scanned beam endoscope are effective imaging devices, they have a limited depth of field because the beam waist distance of the scanned beam 18 of the scanned beam imager 10 and the beam waist distance of the scanned beam of the scanned beam endoscope are fixed. However, superior resolution for a captured image is obtained when the working distance is approximately equal to the beam waist distance. Since the scanned beam imager 10 and the scanned beam endoscope have a fixed beam waist distance and, consequently a limited depth of field, the captured image may not have the quality of resolution desired by the user depending upon the working distance the image capture device is from the FOV or a portion of the FOV being imaged.
Therefore, it would be desirable to provide an image capture device and method, which may be implemented in an endoscope, that can capture higher resolution images of a FOV.